Chrysler 300 Automatic Transmission Mount Guide: 1973-1977
Stop the clunking and vibration in your classic C-Body by addressing its most common driveline weak point.
- Complete new aftermarket mounts are not made for this vehicle; the correct repair is to buy a polyurethane insert.
- Search for parts that fit a 'Mopar C-Body' from 1973-1977, not just 'Chrysler 300'.
- Brands like Energy Suspension and Prothane are the go-to choices for durable polyurethane inserts.
- It is highly recommended to replace the engine mounts at the same time as the transmission mount.
Symptoms of a Failing Transmission Mount
When the transmission mount on your C-Body fails, the signs are hard to ignore. The original rubber has likely become brittle, oil-soaked, or completely separated after five decades of service. Watch for these common symptoms:
- Clunking or Thudding Noises: This is the most common sign. You may hear a distinct "clunk" when you shift from Park to Reverse or Drive, or when you accelerate hard. This sound is the transmission moving excessively and hitting the frame.
- Excessive Vibration: A worn mount can no longer absorb drivetrain vibrations. You'll feel this as a new or worsening vibration in the floor, seats, or steering wheel, especially at idle or while driving.
- Visible Movement: With the vehicle safely secured, have a helper hold the brake and briefly shift into gear. If you can see the transmission lift or twist significantly, the mount has failed.
Why New Aftermarket Mounts Don't Exist for Your 300
You will not find a complete, new aftermarket transmission mount assembly listed for a 1973-1977 Chrysler 300 from major retailers. The market for these specific classic parts is too small for brands like Anchor or Westar to manufacture them. Do not attempt to use a mount listed for a GM vehicle, like an Anchor 2391 or Westar EM-2268, as they will not fit. The solution for C-Body owners is not to find a complete new part, but to rebuild the original one.
Choosing the Right Part: Polyurethane is the Answer
Since complete new rubber mounts are not available, the standard and recommended repair is to reuse your original metal mount bracket and replace the failed rubber portion with a modern polyurethane insert. This is considered an upgrade, as polyurethane is much more durable and resistant to oil and contaminants than the original rubber.
- Polyurethane Inserts (Recommended): Brands like Energy Suspension and Prothane offer polyurethane inserts specifically for Mopar C-Bodies. Forum users report that these are a significant improvement, creating a firmer connection that improves responsiveness without a harsh increase in vibration. You will need to remove the old rubber from your original mount bracket, often by pressing it out or carefully burning it with a torch, before installing the new polyurethane bushing.
- New Old Stock (NOS): You might find an original Mopar mount that has been sitting on a shelf for decades. While this is the most authentic option, these parts are rare, can be very expensive, and the rubber may still be aged despite never being used. Finding one specific to the 1973-1977 models is difficult.
Pro Tip: When searching for a polyurethane insert, broaden your search from "1975 Chrysler 300" to "1973-1977 Mopar C-Body transmission mount." The 300 shares its chassis and many parts with the Chrysler Newport, New Yorker, Dodge Monaco, and Plymouth Gran Fury of the same era.
Estimated Costs for Transmission Mount Replacement
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket (Complete Assembly) | Not Available |
| Polyurethane Insert (Energy Suspension, Prothane) | $40 - $70 |
| New Old Stock (NOS) OEM | $75 - $200+ (If found) |
| Shop Labor for Installation | $150 - $300 |
Frequently Asked Questions (FAQ)
Is this a difficult job to do at home?
For a home mechanic with a good set of tools, including a floor jack, jack stands, and a breaker bar, this is a very manageable job. The process involves safely supporting the transmission, removing the crossmember bolts, and then replacing the mount. The most difficult part is often removing the old, rotted rubber from the original bracket.
Do I need to replace the engine mounts at the same time?
It is highly recommended. The engine and transmission mounts work together as a system. If the transmission mount has failed, the engine mounts are likely in similar condition. Replacing all of them at once ensures the entire drivetrain is properly secured and will save you from doing a similar job again soon.
Will a polyurethane mount make my car vibrate more?
Polyurethane is stiffer than rubber, so it may transmit slightly more vibration into the cabin than a brand-new rubber mount would. However, since your old rubber mount is completely failed, a new polyurethane insert will result in a massive *reduction* in overall vibration and noise. Most classic car owners find it to be a worthwhile upgrade for performance and durability.
Are there any recalls for the transmission mount on my 300?
No. There are no NHTSA safety recalls or Technical Service Bulletins (TSBs) related to the transmission mount for the 1973-1977 Chrysler 300. Any recalls you find online are for much newer Chrysler models.
Technical Specifications
OEM Part Numbers: 2533145
The mount is a 'spool' or 'bushing' type that fits into a steel crossmember bracket. The common repair involves replacing the original rubber bushing with a polyurethane insert, which requires retaining and reusing the original metal bracket.
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.